This Program Project of 20 years brings together six projects and four cores to explore the physiologic and pathophysiologic roles and signaling mechanisms of neuroendocrine peptides. Over the next period we propose to continue our focus on receptors and ligands related to corticotropin releasing factor (CRF),, the principal neuroregulator of the hypothalamic- pituitary-adrenal (HPA) axis which acts within the brain to integrate endocrine, autonomic and behavioral responses to stress. Many human disorders including anorexia nervosa, obesity, drug addiction and depression are associated with perturbation of the HPA axis. Since submission of the last renewal application we and others cloned several variants of a second CRF receptor, CRF-R2, and then we identified a new peptide, urocortin, that is a candidate ligand for some type 2 receptors. Analyses of mice null for both receptor genes and for urocortin are providing insight concerning the specific role of these new molecules. New potent peptide antagonists of CRF have been extensively used in acute studies to probe the physiologic significance and the pharmacologic promise of these important signaling molecules. Project 1 (Vale) cloned a second CRF receptor and a novel candidate ligand, urocortin and will seek to characterize additional ligands detected with the help of Project 6. Ligand binding sites on the initial binding domain of the CRF-R1 and CRF-BP will be characterized. Roles of CRF-R2 and its ligand(s) within the pituitary and mediating central actions of leptin will be studied. Project 2 (J. Rivier) continues to develop CRF antagonists of pharmacologic and fundamental importance and to explore the structural bases of ligands for receptor binding and signal transduction. Project 3 (Lee) has created mice bearing targeted disruptions of CRF-R1, CRF-R2 and urocortin. These strains and those with multiple deletions will be analyzed with focus n the HPA, cardiovascular and autonomic nervous systems and skin. Project 4 (Koob) will continue studies of the roles of CRF, urocortin and their receptors in the mediation of ingestive and stress-related behaviors and will focus on defining the basal and urocortin-induced behaviors of mice null for CRF receptors and ligands. Project 4 (C. Rivier) investigates the respective roles of nitric oxide and carbon monoxide in mediating activation of the MPA axis by neurogenic and systemic stressors. Project 6 (Sawchenko) characterizes the distribution and circuitry of CRF receptors, binding protein and ligands and studies the manner in which those genes are regulated by stress and in mice null for specific CRF receptors and ligands.